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Danger levels avalanches

Avalanches rank among the greatest natural hazards in the Alpine region. They can affect houses, settlements and transportation routes, as well as people engaging in winter sports.

Avalanches are sliding or falling snow masses. They are caused by instabilities in the snowpack. Avalanches occur mostly in steep terrain. The formation of avalanches is facilitated by heavy snowfall, strong wind or a significant rise in temperature. Avalanches can be released naturally (without human intervention) or by people. In 90 percent of cases, avalanches are triggered by the victims. In settlements and on transportation routes, the local authorities ensure the safety of the population. Those who engage in winter sports beyond the boundaries of marked and open pistes, or cross-country ski or hiking trails, are responsible for their own safety.

Danger level 5 (very high danger)
Avalanche triggering probability Many large and multiple very large natural
avalanches are expected, even in moderately steep terrain.
Transportation routes and settlements Acute danger. Comprehensive safety measures.
Outside secured zones Highly unfavourable conditions. Avoid open terrain.
Snowpack stability The snowpack is poorly
bonded and largely unstable in general.
Danger level 4 (high danger)
Avalanche triggering probability Triggering is likely even from low additional loads* on many steep slopes. In some cases, numerous medium-sized and often large-sized natural avalanches can be expected.
Transportation routes and settlements Many exposed sectors are endangered. Safety measures recommended in those places.
Outside secured zones Unfavourable conditions. Extensive experience in the assessment of avalanche danger is required. Remain in moderately steep terrain / heed avalanche run out zones.
Snowpack stability The snowpack is poorly bonded on most steep slopes**.
Danger level 3 (considerable danger)
Avalanche triggering probability Triggering is possible, even from low additional loads* particularly on those steep slopes indicated in the bulletin. In some cases medium-sized, in isolated cases large-sized natural avalanches are possible.
Transportation routes and settlements Isolated exposed sectors are endangered. Some safety measures recommended in those places.
Outside secured zones Partially unfavourable conditions. Experience in the assessment of avalanche danger is required. Steep slopes of indicated aspects and altitude zones should be avoided if possible.
Snowpack stability The snowpack is moderately to poorly bonded on many steep slopes**.
Danger level 2 (moderate danger)
Avalanche triggering probability Triggering is possible primarily from high additional loads*, particularly on those steep slopes indicated in the bulletin. Large-sized natural avalanches are unlikely.
Transportation routes and settlements Low danger of natural avalanches.
Outside secured zones Mostly favourable conditions. Careful route selection, especially on steep slopes of indicated aspects and altitude zones.
Snowpack stability The snowpack is only moderately well bonded on some steep slopes**, otherwise well bonded in general.
Danger level 1 (low danger)
Avalanche triggering probability Triggering is generally possible only from high additional loads* in isolated areas of very steep, extreme terrain. Only sluffs and small-sized natural avalanches are possible.
Transportation routes and settlements No danger.
Outside secured zones Generally safe conditions.
Snowpack stability The snowpack is well bonded and stable in general.
Explanations

* Additional load:

  • high (e.g. group of skiers without spacing, snowmobile/groomer, avalanche blasting)
  • low (e.g. single skier, snowboarder, snowshoe hiker)
  • natural: without human assistance
** Generally explained in greater detail in the Avalanche Bulletin (e.g. altitude zone, aspect, type of terrain)
  • aspect: the compass direction in which a downward slope faces
  • exposed: especially exposed to danger
  • moderately steep terrain: slopes flatter than about 30 degrees
  • steep slopes: slopes with an angle of more than about 30 degrees
  • steep extreme terrain: those which are particularly unfavourable as regards slope angle (usually steeper than about 40°), terrain profile, proximity to ridge, roughness of underlying ground
“conditions” refers exclusively to the avalanche danger. The avalanche bulletin only rarely remarks on the condition of the snow (powder snow, corn snow, breakable crust) and weather conditions (fog, storm force winds), which are also potentially dangerous in some circumstances.

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